In the Chanuka story, given that the oil would naturally have lasted for one day, wasn't only the continued burning on the second through seventh days miraculous, and shouldn't we therefore only celebrate for seven days?

It was said by a play on words that R' Moshe Feinstein's native city, Starobin, had "one hundred rabbis" (in Russian, "sta rabin") - in other words, one hundred laymen (baalei batim) who were fully knowledgeable enough that they could have served as community rabbis elsewhere.

In the second בית המקדש, the היכל building (including the אולם) was 100 אמות tall by 100 אמות long by (at its widest point) 100 אמות wide. (Does that count as three on the list?) (Source: mishnayos Midos.)

A paper, a different version of which was apparently published in the J. Hal. Contemp. Soc., quotes the Tzemach Tzedek (Lubavitch, not Nikolsburg) as saying that 100 amos (cubits) is the distance water must travel underground before it comes up again to be considered a spring.